Recovering hydrocarbons from subterranean zones typically involves drilling wellbores.
Wellbores are made using surface-located drilling equipment which drives a drill string that eventually extends from the surface equipment to the formation or subterranean zone of interest. The drill string can extend thousands of feet or meters below the surface. The terminal end of the drill string includes a drill bit for drilling (or extending) the wellbore. Drilling fluid usually in the form of a drilling “mud” is typically pumped through the drill string. The drilling fluid cools and lubricates the drill bit and also carries cuttings back to the surface. Drilling fluid may also be used to help control bottom hole pressure to inhibit hydrocarbon influx from the formation into the wellbore and potential blow out at the surface.
Bottom hole assembly (BHA) is the name given to the equipment at the terminal end of a drill string. In addition to a drill bit a BHA may comprise elements such as: apparatus for steering the direction of the drilling (e.g. a steerable downhole mud motor or rotary steerable system); sensors for measuring properties of the surrounding geological formations (e.g. sensors for use in well logging); sensors for measuring downhole conditions as drilling progresses; one or more systems for telemetry of data to the surface; stabilizers; heavy weight drill collars, pulsers and the like. The BHA is typically advanced into the wellbore by a string of metallic tubulars (drill pipe).
Modern drilling systems may include any of a wide range of electronics systems in the BHA or at other downhole locations. Such electronics systems may be packaged as part of a downhole probe. A downhole probe may comprise any active mechanical, electronic, and/or electromechanical system that operates downhole. A probe may provide any of a wide range of functions including, without limitation, data acquisition, measuring properties of the surrounding geological formations (e.g. well logging), measuring downhole conditions as drilling progresses, controlling downhole equipment, monitoring status of downhole equipment, measuring properties of downhole fluids and the like. A probe may comprise one or more systems for: telemetry of data to the surface; collecting data by way of sensors (e.g. sensors for use in well logging) that may include one or more of vibration sensors, magnetometers, inclinometers, accelerometers, nuclear particle detectors, electromagnetic detectors, acoustic detectors, and others; acquiring images; measuring fluid flow; determining directions; emitting signals, particles or fields for detection by other devices; interfacing to other downhole equipment; sampling downhole fluids, etc. Some downhole probes are highly specialized and expensive.
Downhole conditions can be harsh. Exposure to these harsh conditions, which can include high temperatures, vibrations, turbulence and pulsations in the flow of drilling fluid past the probe, shocks, and immersion in various drilling fluids at high pressures can shorten the lifespan of downhole probes and increase the probability that a downhole probe will fail in use. Supporting and protecting downhole probes is important as a downhole probe may be subjected to high pressures (20,000 p.s.i. or more in some cases), along with severe shocks and vibrations. Replacing a downhole probe that fails while drilling can involve very great expense.
The following references include descriptions of various downhole probes and centralizers that may be useful for supporting a downhole probe in a bore within a drill string: US2007/0235224; US2005/0217898; U.S. Pat. Nos. 6,429,653; 3,323,327; 4,571,215; 4,684,946; 4,938,299; 5,236,048; 5,247,990; 5,474,132; 5,520,246; 6,429,653; 6,446,736; 6,750,783; 7,151,466; 7,243,028; US2009/0023502; WO2006/083764; WO2008/116077; WO2012/045698; and WO2012/082748.
US 2007/0235224 describes an elastomeric tubular liner that is secured to the inner surface of a tubular member. The tubular liner is molded in place in the bore of the tubular member. The tubular liner can be removed by drilling, burning or melting.
US 2005/0217898 describes a drill collar for damping downhole vibration in the tool-housing region of a drill string. The collar comprises a hollow cylindrical sleeve having a longitudinal axis and an inner surface facing the longitudinal axis. Multiple elongate ribs are bonded to the inner surface and extend parallel to the longitudinal axis.
There remains a need for cost-effective and easily serviceable ways to support downhole probes, which may include electronics systems of a wide range of types at downhole locations in a way that provides at least some protection against mechanical shocks and vibrations and other downhole conditions.